1. Field of the Invention
The present invention relates to a motor-driven fuel pump for pumping fuel from a fuel tank through a pressure regulator and an injector into an internal combustion engine.
2. Description of the Prior Art
An engine fuel injection system has been known which includes a motor-driven fuel pump adapted to be disposed in a fuel tank so as to pump liquid fuel from the tank through a pressure regulator and a filter to an injector which is operative to inject the fuel into an engine. A typical prior art motor-driven fuel pump of the class specified has been desinged to provide a discharge pressure of more than 200 Kpa. The discharge requirement for the prior art fuel pump was solely to meet the lower limit of the discharge pressure. In designing the prior art fuel pump, the designer was not required to pay any particular attention to the upper limit of the pump discharge.
Recent automotive fuel injection systems manufactured by automobile manufacturers, however, need fuel pumps to be operated to provide discharge pressure of medium levels around 100 Kpa. Because of this greatly lowered fuel pump discharge pressure, the pressure regulators of associated fuel injection systems are required to provide greatly increased pressure-regulating abilities so as to more strictly control the upper and lower limits of the pressure of fuel to be injected. However, pressure-regulators which satisfy this requirement are very difficult to manufacture and tend to be very expensive.